After perusing this form, conflicting views can emerge. Please confirm or deny (based, if possible on actual experience, not theory):

1) it's not worth striping or putting 2 2TB 7200rmp drives in a RAID0, if significant media playback performance improvement is the goal.

2) PPRO project files and OS swap file should not be on the boot disc

3) media cache files should be on neither the boot disk nor the media disks

If all of the above is true, that means at least 4 disks(?)

In my case, I planned on 3 drives, to start: 1 TB system drive for boot, software, project files, swap file, and media backups, and 2 2TB media drives, one of which would have to host the media cache. Does this make sense or not? Footage is likely to be AVC Intra, at 100-150mbs, and for straight cuts narrative material. Filters yes, but not much in the way of compositing etc. Thanks.

3) export drive same as above but 2 and 3 can be combined in a large (8+) drive array on a good controller

4) external archival/storage (even if you have raid 5,6)

questions 2 and 3 i am not allowed to comment on (Eric will shoot me, wait am i not the boss?) but i will say there is a lot of MYTH floating around.. guys with 5+ drive letters are ill-informed or are left over from many yrs ago advice.

1) it's not worth striping or putting 2 2TB 7200rmp drives in a RAID0, if significant media playback performance improvement is the goal.

False.

2) PPRO project files and OS swap file should not be on the boot disc

Project files on the Boot disk are OK, if you have the space. Swap file is always on the boot disk, isn't it? You don't have a choice with Mac. But, anyway, that's why you always want adequate free space on your boot disk: for the swap file.

3) media cache files should be on neither the boot disk nor the media disks

Again, if you have space to spare, it's OK to use the boot disk. However, if your media disk is a RAID 0, anything you put there will read and write faster, and therefore that would be my choice.

If all of the above is true, that means at least 4 disks(?)

Not all the above is true. If your needs are for AVCHD, which is HIGHLY compressed low data rate codec, I don't think you even need a RAID. You can probably get by with a boot drive, and a single fast internal drive (or external on eSATA or USB3), unless you expect to do a half dozen layers in real-time, in which case you're going to need a super-fast multi-core CPU more than fast drives, due to the decompression demands from the codec.

AVC-Intra is a more drive intensive codec. I haven't used it yet, but it does 50 or 100Mb/s. If you have a two-7200 drive RAID 0 for media, that's going to give you more options for formats that require more bandwidth.